1. Field of the Invention
The invention concerns a method for managing resources of a link, which may be a wireless link, in a communication network in particular a network comprising wired communication busses interconnected with the help of wireless links.
2. Description of Related Art
In a network comprising a plurality of interconnected transmission media, the bandwidth available over each transmission medium may not necessarily be the same.
If one considers for example two IEEE 1394 wired serial busses connected together using a 5 GHz ETSI BRAN HiperLAN 2 wireless link, the bandwidth available on each of the wired busses can be of 100 Mb/s or more, while the bandwidth available over the wireless link may be limited to 30 Mb/s. Consequently, the wireless link constitutes a bottleneck for connections using this link.
FIG. 1 is a diagram of one example of such a network. The network comprises two busses 11 and 12, connected to source device 13 and sink device 14, respectively to sink device 15 and source device 16. Source device 13 is for example a digital VCR, while sink devices 14 and 15 are displays and source device 16 is a tuner. Bus 11 is also connected to a portal 17, while bus 12 is connected to a portal 18, both portals forming a wireless link between busses 11 and 12. It is supposed that the wireless link is transparent to devices 13 to 16 at the level of IEEE 1394, i.e. these devices have the impression that they are on the same physical bus.
Supposing the available bandwidth on the wireless link is of 30 Mb/s, a first connection of 20 Mb/s is established between the VCR 13 and the display 15. A second connection between tuner 16 and display 14 can be established, since the link is transparent to devices 16 and 14, but if the bandwidth required for this second connection is greater than the remaining wireless bandwidth, the display 14 will not display proper pictures, if any at all. As far as the application having built the second connection is concerned, the connection was nevertheless established without incident at the IEEE 1394 level, because of the transparency of the link at that level.
The document EP-A-0 933 900, discloses a method for interconnecting 1394 busses by a 1394 bridge. In this document, each bus and the bridge consists of an independent bus, and the method allow two nodes from different bus to make bandwidth and channel reservation to allow an isochronous communication between the two nodes. This method consists of making the three corresponding bandwidth reservation on each independent bus, the one hosting the emitting node, the bridge and the one hosting the receiving host.
Contrary to what is disclosed in this document, we are in the case where the link that connects busses is transparent. That means, that a node on one bus sees all the nodes on the interconnected busses as belonging to the same network.
The object of the invention is a method for managing resources of a link in a communication network comprising at least two busses connected to the link to form a network, wherein the network forms a single virtual bus regarding the protocol used by a bus, said method comprising the steps of:                providing a link-aware application in a node of the network for obtaining link resource reservation information,        for establishment of a connection between devices over the link, accessing said information, and        determining whether the connection can be established as a function of this information.        